Hello,
If you want to have two different sites, you will need to have two different licenses.
In case you migrate your site from one domain to another, you can use your license. You will need to enter ThemeForest account and deactivate the domain you are not going to use any more.
You can activate your license twice for one and the same site, if you want to have live and testings site.
If you have any questions please feel free to contact us.
Best Regards